This invention relates to a multicolor gravure rotary press comprising a train of monochromatic printing units each allotted for performing a different color printing on an elongated sheet. More specifically, this invention relates to a multicolor gravure rotary press comprising a train of monochromatic printing units each consisting of an upper structure including an impression roll and a lower structure including a plate cylinder and an ink device, each said upper structure being integrally connected to and suspended from a main frame the end legs of which at the opposite extremes with respect to the sheet-feeding direction are fixed to the floor of the shop, and each said lower structure when raised, being brought into fast union with the associated upper structure.
The most commonly used conventional multicolor gravure rotary press consists of a train of individual printing units each allotted for performing a different color printing, thereby finally causing multicolored patterns to appear on a sheet in the form of multicolor combinations. These individual printing units are separate from each other and each is fixed to the floor of the shop.
With a view to facilitating the work of changing printing plates, the entire plate cylinder bearing the printing plate is ordinarily detached from the body of printing unit, and then another plate cylinder prepared in advance is inserted into the printing unit. Thus, the time required for completion of the printing work is accordingly shortened.
In moving and changing the plate cylinder a carrier is ordinarily used because of the relatively heavy weight of the plate cylinder.
Sometimes a carrier is integrally connected with the body of the plate cylinder. In a still better arrangement, the plate cylinder, the ink device and other auxiliary parts are built into the carrier. These arrangements make it easy to replace the printing plate, and at the same time advantageously give the operator plenty of time to clean the printing plate and to adjust the various parts of the plate cylinder after it has been detached from the printing unit. The combination of the carrier and the printing cylinder makes it easier to remove the plate cylinder than the use of a separate carrier. There has, however, been no reliable and easy means for bringing the carrier-and-plate cylinder assembly into engagement with the main frame to which the impression roll is fixed. One attempt in this direction has been the provision of a revolving turret, a component which itself is entirely unnecessary for a printing machine. This turret is provided on the main frame which supports the impression cylinder. A carrier bearing a plate cylinder is placed on the turret, and then the turret is rotated to bring the carrier into a position at which the printing cylinder is aligned to and in contact with the impression roll, thereby making the printing machine ready for operation. This arrangement makes it easy to align the plate cylinder-and-carrier assembly with the impression roll, but still requires laborious work in attaching and detaching the plate cylinder from the printing unit.
As is readily understood from the above, the cost of the conventional multicolor printing machine comprising a train of separate monochromatic printing units, will increase with the number of different colors to be printed, and also, disadvantageously, the conventional multicolor printing machine requires laborious and time-consuming work in changing the printing plates. With the conventional printing machine it is practially impossible to shorten the amount of idle time or reduce the amount of work involved in the printing operation.
One object of this invention is to provide a rotogravure printing system which has a structure so simple as to permit the reduction of installation cost and which, at the same time, permits easy replacement of the printing cylinder so as to improve the working efficiency of the printing machine.
Another object of this invention is to provide a rotogravure printing system of a structure which makes it possible to replace a used plate cylinder with a standby in a very short time and also permits mechanized transport of plate cylinders by use of guide tracks on the floor of the shop.